A wax melt is finished when it is no longer producing enough fragrance for you, not when the wax disappears. This surprises people who are used to candles, because a warmer can leave a dish full of wax even after most of the scent has been released.
Let the wax fully warm before judging it. If you can barely smell the fragrance after the wax has melted and you have been in and out of the room, it may be spent. You can then let the wax cool and remove it using the method recommended for your warmer. Do not pour hot wax into a sink or drain.